Date: Wed, 6 Nov 2019 18:18:38 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: David Wheeler <dwheeler@dgitsystems.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	pgsql-performance@lists.postgresql.org,
	Cameron Redpath <credpath@dgitsystems.com>
Subject: Re: Slow planning, fast execution for particular 3-table query
Message-ID: <20191107001838.GG4999@telsasoft.com>
References: <15855.1572843659@sss.pgh.pa.us>
 <175BE386-F861-4064-8B5D-93E63BD90F13@dgitsystems.com>
 <20191106225945.GE4999@telsasoft.com>
 <CAKJS1f8L4QHyfj4qJsz2r6QEfcTMqx2MRPiC0PXuKZx0CjRZug@mail.gmail.com>
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On Thu, Nov 07, 2019 at 01:15:30PM +1300, David Rowley wrote:
> On Thu, 7 Nov 2019 at 11:59, Justin Pryzby <pryzby@telsasoft.com> wrote:
> >
> > On Mon, Nov 04, 2019 at 03:04:45AM +0000, David Wheeler wrote:
> > > Postgres version 9.5.19
> > > Each of the tables has between 3-4 indexes, and all the indexes include tid as first parameter.
> 
> > But note that index definition will be prohibited since:
> >
> > https://www.postgresql.org/docs/9.6/release-9-6.html
> > |Disallow creation of indexes on system columns, except for OID columns (David Rowley)
> > |Such indexes were never considered supported, and would very possibly misbehave since the system might change the system-column fields of a tuple without updating indexes. However, previously there were no error checks to prevent them from being created.
> 
> David will have meant the user column named "tid" rather than the
> system column named "ctid".

Ah.  And David must have meant David W :)

Justin